Discovery of novel 20S-protopanaxadiol derivatives in alleviating sepsis-associated liver injury by modulating p65/p50 activity

Sepsis-associated acute liver injury (SALI) is a common and severe complication of sepsis, contributing directly to disease progression and increased mortality. In this study, a series of 20S-protopanaxadiol (20S-PPD) derivatives with anti-inflammatory properties were designed and synthesized. Structure-activity relationship (SAR) analysis at key sites, based on nitric oxide (NO) inhibition assays, identified 9a as the most potent anti-inflammatory derivative. Remarkably, 9a alleviated SALI in a concentration-dependent manner, demonstrating superior efficacy to the glucocorticoid drug hydrocortisone sodium succinate. This protective effect was achieved by suppressing abnormal activation of the NF-κB and MAPK signaling pathways, without activating Glucocorticoid Receptor (GR) signaling. The apparent paradox between the effect of 9a on IκB degradation and its anti-inflammatory activity prompted further investigation. Pull-down assays further identified the p65-p50 heterodimer as a target of 9a. Molecular docking and cellular thermal shift assay (CETSA) confirmed that 9a bound to the p50 subunit, impairing the DNA-binding capacity of the p65-p50 heterodimer and consequently exerting anti-inflammatory activity. This study provides detailed SAR insights into 20S-PPD derivatives for anti-inflammatory drug development and offers new perspectives on their mechanism of action in mitigating SALI.